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Posted: Thu Jun 11, 2009 7:09pm

Post Subject: boat wiring problem

hi tony have now sorted rev counter problem ,fitted s/h panel. thanks for your input. my problem now is that the horn and tunnel light are not working. when i push the horn button the warning light for the lamp lioghts up i suspect an earthing fault but dont seem to be able to follow the circuit. i tried wiring an earth direct to the hull and the light and horn worked briefly then stopped again . i was also told this was not advisable.can you confirm thanks bob jones


Posted: Fri Jun 12, 2009 10:43am

Post Subject: boat wiring problem

Dear Bob, The horn and tunnel lamp are wired by the boatbuider, starting at the relevant switches. The rest of the panel is usually wired by the engine mariniser so I fear you will need to start tracing cables to see how it is wired. I would use a muti-meter set to 200 ohms or better still beep/buzz plus a long piece of cable the length of the boat so you can locate and identify the switch end of each positive cable. Once you have done that you can connect them to the relevant switches. It is not unknown for boatbuilders to save money by using one cable for the negative run from both the horn and tunnel lamp and from your description I suspect its this cable that is causing the problem. Again using the meter as above should enable you to locate the cable at the back of the boat. I wonder if you have blown a fuse? It is bad practise to earth to the hull and if you can not locate the stern end of the negative cables it would be better to run a separate earth, but make sure it can carry about 6 to 8 amps with no more than 0.5V voltdrop. If you really pushed me I would have to say that if you are going to use the hull for an earth then those two items would be the least potentially damaging because they are rarely used and when they are not for long periods. However there is a potential corrosion penalty so I would not do it. Tony Brooks

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